While the present invention of a coating apparatus can be effectively used in a plurality of different tube coating uses, it will be described for clarity as used in a tube or photoconductive drum used in a Xerographic system.
By way of background, in marking systems such as xerography or other electrostatographic processes, a uniform electrostatic charge is placed upon a photoreceptor belt or drum surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the drum photoreceptor surface. The toner may be in dry powder form or suspended in a liquid carrier. The charged toner, being electrostatically attached to the latent electrostatic image areas, creates a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to an intermediate transfer belt or to a final support material, such as paper.
In some of these electrostatic marking systems, a photoreceptor belt or drum surface and an intermediate transfer belt (ITB) are generally arranged to move in an endless path through the various processing stations of the xerographic marking process. In this endless path, several xerographic-related stations are used having a plurality of photoconductive drums which become abraded and worn partly because of contact with their components in the system, such as belt configurations, such as transfer belts, pre-fuser belts, cleaning blades or belts and the like. Each of these drums is constantly exposed to friction, especially in high speed systems, the drum needs to be frequently replaced. Also, since the photoreceptor drum is reusable once the toner image is transferred, the surfaces of these belts are constantly abraded and cleaned by a blade and/or brushes and prepared to be used once again in the marking process. In U.S. Patent publication U.S. 2008/0199216 (incorporated by reference herein) a problem in drum xerographic usage is noted, i.e. “When electrostatographic drums are cleaned by doctor type cleaning blades rubbing against the imaging surface to remove residual toner particles remaining on the imaging surface after toner image transfer to a receiving member, a high pitched ringing, squealing, squeaking, or howling sound can be created which is so intense that it is sometimes intolerable for machine operators. This is especially noted in drum type imaging members comprising a hollow cylindrical substrate.
Under normal operation in a printer/copier, a drum photoreceptor can emit a noticeable and objectionable sound. The cause of this noise can be due either to the cleaning or charging mechanisms. If a BCR (bias charging roll) is utilized to charge the photoreceptor, the AC voltage applied between the BCR and a photoreceptor can produce a “forced” mechanical vibration at the AC frequency. Alternatively, slip-stick motion of the cleaning blade against the photoreceptor surface can drive a mechanical resonance at the slip-stick frequency. There are several known methods to combat this problem, each with its own disadvantages.    A. One can simply make the P/R tube wall thicker. This stiffens the tube which in turn reduces the amplitude of the vibrations/sound. Additionally, the added mass changes the natural resonant frequency of the tube. The down side is that the added wall thickness uses more aluminum and costs more.    B. One can insert “silencers” into the interior of the P/R tube to dampen the mechanical vibration and reduce the amplitude of the noise. See for example, U.S. Pat. No. 5,722,016“Electrostatographic Imaging Member Assembly”. This is what we, Xerox, currently do with the 30 mm diameter P/R tubes for the Imari Family of machines. This approach costs more than $1.05 per P/R for the assemblies used in the Workcentre Pro 32 and related products.    C. One can coat the interior of the P/R tube with an appropriate acoustic dampening compound such as a silicone rubber, latex caulk, soft UV curable rubber, etc. This concept has been successfully demonstrated. It functions equivalent to or better than (up to a total of 3) inserted “silencers” in recent testing. Furthermore, this approach does have the potential to be significantly lower cost than prior methods. For further discussion of this approach, refer to earlier noted U.S. Publication No. 2008/0199216A1 “Method for Acoustic Dampening of Photoreceptor Drums”.
The application of such a compound to the interior of the P/R tube does pose some challenges both in how to apply the coating and where/when in the manufacturing process is the coating applied. Initial thoughts were to use a process similar to flow coating, but on the interior of the P/R tube wherein the P/R tube would be rotated and a continuous touching spiral of material would be applied. However, after consideration of that concept it was believed that process would take too long and would not be compatible with the current 9 second cycle time for each station on the existing P/R production facility. This invention addresses the important concern—How to apply an acoustic dampening compound to the interior of a photoreceptor tube in a time period commensurate with a total cycle time of under 9 seconds.
Internal “Silencers” have been utilized in photoreceptor P/R tubes or drums to quench noise for quite a while; there are numerous patents related to the concept. Recently, the manually internally applied acoustic dampening coating was disclosed; see Xerox earlier noted Patent Publication 2008/0199216A1—“Method for Acoustic Dampening of Photoreceptor Drums” by Steven C. Hart & Patricia Campbell (now a pending U.S. patent application). Initial examples were created in this publication using a caulk gun and spatula to apply the coating to the tubular interior of large (84 mm) diameter photoreceptors. Hand application via a spatula is not feasible as a large scale manufacturing technique; additionally, it is difficult, if not impossible, to do inside a smaller 30 mm diameter photoreceptor. Subsequently, a crude apparatus was fabricated and used to hand coat the interior of 30 mm diameter photoreceptors. Machine testing of these samples indicated that the (un-optimized) internally applied acoustic dampening coating performed equal to or slightly better than the old style non-coated “silencers.” Additionally, it is desirable to provide an assembly to accomplish the coating operation within a total cycle time of under 9 seconds so as not to slow down the P/R production line.